1. Field of the Invention:
The present invention relates to a structure in which a fine wire being the lead of an electric component, particularly a fine wire having a conductor diameter of or below 100 .mu.m is soldered on a conductor pattern. It also relates to a method of soldering the fine wire, and an apparatus therefor.
2. Description of the Prior Art:
In connecting a conductor pattern on the substrate of an electric component and an insulator-coated fine wire the core conductor of which has a diameter of 100 .mu.m or so and the surface of which is treated with a synthetic resin, there has heretofore been often employed a method wherein as illustrated in FIG. 9, the insulator-coated fine wire 3 is arranged on the conductor pattern 1 previously formed with a solder layer 2 about 5 .mu.m thick, and the core wire 4 of the insulator-coated fine wire 3 is thereafter connected by reflowing through Joule heat generated in such a way that a resistor tip 6 depressed on the upper side of the fine wire 3 is energized by a welding source 7. On this occasion, the synthetic-resin insulating coating 5a of the insulator-coated fine wire 3 is melted or vaporized off by the heat generation of the resistor tip 6, and only the core wire 4 is welded into the solder layer 2 as shown in FIG. 10. A plan view of the external appearance of the parts connected as described above, is shown in FIG. 11. Symbol 5 b denotes the solidified residue of the synthetic-resin insulating coating which has been melted at the stage of the reflowing connection.
Relevant to the joining method of this type are techniques disclosed in Japanese Patent Application Publication No. 15856/1970, Japanese Patent Application Laid-open No. 210694/1982 and Japanese Patent Application Laid-open No. 134491/1985.
The prior art stated above is chiefly directed toward the connection of the insulator-coated fine wires whose conductors have diameters larger than 100 .mu.m. It does not take into consideration a fine wire whose conductor has a diameter of or below 100 .mu.m, and it has posed such a problem that the bonding strength of the connected portion lowers due to the deformation or damage of the ultra-fine wire ascribable to the pressure application of the resistor chip. For this reason, the ultra-fine wire has hitherto been manually joined with a solder and by a soldering iron. The manual microscopic joining operations, however, require the aptitude and skill of an operator and have necessitated a large number of man-hours. Further, the manual operations have been problematic as to reliability.